Junk-food taxes have mixed effects on obesity and junk-food consumption. We build a theoretical model to explain empirical results and better understand how to address the obesity crisis. In our framework, hand-to-mouth consumers make an intertemporal choice between junk-food consumption and weight loss. Their choice depends on calorie consciousness, which is influenced by perceived after-tax relative prices and educational attainment. Thus, a junk-food tax modifies consumers’ intertemporal choice both through their budget constraint and calorie consciousness. As a result, the effect of the tax on body weight reflects competing income, intertemporal substitution, and calorie-consciousness effects. The model explains empirical observations such as the recent rise in obesity and differences in weight outcomes for different income levels. The model explains circumstances under which junk-food taxes can be effective or ineffective to reduce body weight as well as differences in elasticities of high-calorie food consumption for high- and low-income earners.

垃圾食品税对肥胖和垃圾食品的消费有不同的影响。我们建立理论模型来解释经验结果，并更好地了解如何解决肥胖危机。在我们的框架中，口口相传的消费者在垃圾食品消费和减肥之间做出了跨时代的选择。他们的选择取决于卡路里的意识，这受感知的税后相对价格和受教育程度的影响。因此，垃圾食品税会通过预算约束和卡路里意识来改变消费者的跨期选择。结果，税收对体重的影响反映了相互竞争的收入，跨期替代和对卡路里的了解。该模型解释了经验性观察结果，例如最近肥胖症的上升以及不同收入水平的体重结局的差异。